From: Martin Schwidefsky <schwidefsky@de.ibm.com>
Date: Tue, 21 Jul 2009 18:25:05 +0000 (+0200)
Subject: timers: Cache __next_timer_interrupt result
X-Git-Tag: v2.6.32-rc1~168^2~30
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=97fd9ed48ce2b807edc363bef3e817aeeb5cd5e6;p=pandora-kernel.git

timers: Cache __next_timer_interrupt result

Each time a cpu goes to sleep on a NOHZ=y system the timer
wheel is searched for the next timer interrupt. It can take
quite a few cycles to find the next pending timer.

This patch adds a field to tvec_base that caches the result of
__next_timer_interrupt.

The hit ratio is around 80% on my thinkpad under normal use, on
a server I've seen hit ratios from 5% to 95% dependent on the
workload.

-v2: jiffies wrap fixes

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Venki Pallipadi <venkatesh.pallipadi@intel.com>
LKML-Reference: <20090721202505.7d56a079@skybase>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---

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